According to fossil evidence, life on earth is speculated to have begun roughly 3.7 billion years ago. Today, the earth is home to countless species – ranging from microscopic microbes to gargantuan blue whales. The diversity of life is so vast, that there are many species, yet to be discovered. For instance, the giant squid (Architeuthis dux), was nothing more than a sailor’s tall tale until an actual specimen was recorded on video in 2004.
Similarly, there are many organisms that are yet to be identified or discovered. However, we do need a system to classify the organisms that we do know about. This is due to the fact that the same organism or its variations may exist across multiple locations around the planet. And these organisms are given different names according to the locations, though all are biologically the same organism.
Hence, the idea of biological classification was put forward. We shall explore what is biological classification and its basis of classification in detail.
What is Biological Classification
Biological classification is the scientific procedure of arranging the organisms in a hierarchical series of groups and sub-groups on the basis of their similarities and dissimilarities. Many biologists have contributed to this method of classification, which took years for researchers to decide the most fundamental characteristics for the classification.
Basis of Classification
The history of biological classification began with Aristotle, the Greek philosopher, who is often called the father of biological classification. He described animal classification based on their habitat, i.e., air, water and land. He was the first person to recognize the need for groups and group names in the study of the animal kingdom.
Later, biologists started to work on the classification of living organisms based on their characteristics. Characteristics can be explained in many ways. A group of organisms is similar enough to be classified together by certain characteristics. Characteristics are the appearance/form and behaviour/function of something. These characteristics decide which organism will be placed in which group.
For example, a dog has limbs, but a snake doesn’t. A dog and a snake can move, but plants cannot. These are the characteristics of different organisms. These behaviours classify them into different groups. But which character should be the fundamental form or function? As per the above example, how should a dog be classified- whether on the basis of body design or its locomotion? Therefore, this was not successful
In the mid-1700s, Carolus Linnaeus, a Swedish physician and botanist, published several books on different species of plants and animals. According to his system of classification, he grouped organisms according to common physical traits and developed the two-part binomial taxonomy system of categorizing organisms according to genus and species. This type of classification was effective. Later, his work was combined with the work of Charles Darwin, forming the foundation of modern taxonomy.
Today, some of the characteristics which are used today to classify organisms are as follows:
- Type of cell – Prokaryotic or Eukaryotic cell.
- Number of Cells – Unicellular or Multicellular.
- Mode of Nutrition – Autotrophs (Photosynthetic) or Heterotrophs (Non-photosynthetic).
- The level of organization and development of organs.